Traditionally, most hearing aids capture sound through a microphone that delivers an amplified and/or modified version of the sound signal into the user's ear canal through a suitable electrical-to-audio transducer, e.g., a small speaker. The proximity of the microphone to the transducer can disadvantageously produce audio feedback from the transducer to the microphone. The present invention relates to a hearing aid system that includes a transducer configured for implantation to project acoustic energy into a patient's outer ear canal in combination with a remote microphone.
The solution in the past for eliminating feedback has been to occlude the ear canal via an ear mold such that the transducer is located distally to the occlusion, while the microphone is located proximally to the occlusion. Unfortunately, occlusion of the ear canal can create several disadvantages for the user, such as reverberation and physical discomfort, and is a major cause for non-use of traditional hearing aids by the hearing impaired.
In addition, it is desirable to make hearing aids less visible, as most users perceive the aid as imparting a negative stigma. Thus, hearing aids are continuously becoming smaller and have moved from behind the ear into the outer ear and into the canal of the ear.
It is known in the art to connect the retro-auricular space (space behind the pinna of the ear) to the ear canal via a hollow titanium tube that is permanently placed into a tunnel through the tissue. See, e.g., U.S. Pat. No. 6,094,493, which patent is incorporated herein by reference. In one embodiment of the '493 patent, an amplification hearing aid is connected to the proximal (retro-auricular) end of the tube. The hearing aid is thus located behind the pinna of the ear and a transducer sends the amplified sound signal through the tube into the ear canal. This concept, which has been commercialized by Auric® Hearing Systems, Inc. of Charlotte, N.C. as the RetroX technology, allows a certain degree of amplification without feedback and without the need for occlusion of the ear canal. In another embodiment of the '493 patent, the microphone, transducer, electrical and electronic components are installed in the tube.
Although hearing amplification via the '493 patent is achieved without occluding the ear canal, the tunnel leaves a continuous opening which is subject to infection and inflammation. In addition, although the described invention provides improvements over traditional hearing aids, the user still has the burden of maintenance associated with body-mounted hearing devices. These burdens include (1) frequent replacement of a tiny battery within an enclosed battery chamber, (2) removal of the miniature device from its mounting in the retro-auricular space for showering and water sports, and (3) expelling water from the hollow tubular element after exposure to moisture.
Improvements to the system referenced above have been described in patent applications by Advanced Bionics, Inc. However, the tunnel providing the continuous opening between the retro-auricular space and the ear canal remains, with its associated risks for infection and inflammation.
In U.S. Pat. No. 5,430,801, the use of a silicone tube “sound conductor” with similar infection and inflammation risks is disclosed. The sound conductor is physically attached to the electronics package of the hearing aid, and directs the output from the electronics into the ear canal by extending through the skin of the retro-auricular space. A microphone is positioned in the conchal bowl of the user, and the electronics package is connected to the microphone and held behind the pinna via a piercing through the cartilage of the concha.
Several concepts for implanting all or part of the hearing aid into the middle ear have been developed. Such approaches couple an amplified and processed version of the sound signal to structures of the middle ear mechanically, thereby reducing feedback without occlusion of the ear canal. Such systems also reduce or eliminate visibility of the hearing aid, and have the potential for improving user comfort. Disadvantageously, however, such middle-ear-coupled systems require, inter alia a significant surgical procedure.